NORTH KOREA: Mystery surrounds a massive explosion that shook North Korea late last week causing a four-kilometre-wide mushroom cloud. However, experts do not believe the blast was related to the country's nuclear weapons programme.
The whole North Asian region around the Korean peninsula is jittery because of the Stalinist country's nuclear weapons ambitions.
The blast was first picked up by satellite and probably happened late on Wednesday or early on Thursday morning.
US Secretary of State Colin Powell said Washington did not believe North Korea had conducted a nuclear test.
The South Korean news agency, Yonhap, said the explosion happened in a county called Kimhyungjik in the remote province of Ryanggang near the Chinese border.
The blast, which left a huge crater, took place near missile bases and was much bigger than the train explosion in April which killed scores of people. That explosion also took place on the Chinese border.
"There was no indication that was a nuclear event of any kind. Exactly what it was, we're not sure," Mr Powell told NBC Television.
"They haven't conducted tests to the best of our knowledge and belief, and the activity reported today is not conclusive that they are getting ready to do one or not," he said.
There have been reports that the US government has received intelligence suggesting North Korea was preparing its first nuclear weapons test explosion.
Washington and Pyongyang are currently in a stand-off over North Korea's plans to develop nuclear weapons. A nuclear weapons test would seriously up the ante.
Washington reckons North Korea already has possibly two nuclear devices, but that it lacks a reliable way of targeting the warheads.
In relation to last week's explosion, experts say that if there had been a test, it would have been picked up by nuclear agencies all around the world.
Analysts believe it is unlikely the North Koreans would try to test any weaponry ahead of a visit by a senior Chinese delegation this week to deliver a message promising economic aid to Pyongyang.
China is North Korea's only real friend in the region.
Thursday was the 56th anniversary of North Korea's founding. The reclusive communist state often stages extravaganzas to mark important anniversaries, although it was not clear if this could have been linked to the explosion.
According to South Korean newspaper reports, the blast happened around 10 kilometres southwest of the Yongjori missile base, around 30 kilometres away from the Chinese border, in a restricted area.
News of the blast coincided with fresh efforts by South Korea, Japan, China, Russia and the United States to persuade North Korea to resume talks on its nuclear ambitions. Washington wants Pyongyang to fully disclose all of its nuclear activities and allow outside monitoring before it receives any foreign aid.
There have been different possible explanations for the blast, including a forest fire or an explosion at a munitions dump or a failed missile test.
